Astronomical instruments

Visitors queue to view the transit of Venus on 8 June 2004 through a telescope and solar filter in front of the Royal Observatory, Greenwich. ©National Maritime Museum, Greenwich, LondonTuesday June 8 was a special day as a 'transit of Venus' was visible from the UK. These are very rare and this year was the sixth to be viewed in recorded history. A 'transit of Venus' is when the planet Venus can be seen from Earth passing in front of the Sun's disc. It occurs twice about every 113 years.

The next transit will be in 2012 and is only partly visible from the UK. The pair of transits after that will be in the distant years of 2117 and 2125. The last pair were in 1874 and 1882.

Ideal conditions

WARNING: Looking straight at the Sun with the naked eye or with equipment not designed to do so is extremely dangerous with the very real risk of permanent damage to your eyes. Sun glasses are absolutely no protection.

Viewing the transit of Venus using specially made solar filter glasses, sometimes called 'eclipse shades', 8 June 2004.The UK enjoyed good weather earlier in the summer and the morning of June 8 brought ideal conditions at the Royal Observatory, Greenwich and across the southern half of the UK.

People at the Observatory queued to look at the transit through a solar viewer set on a tripod. The transit began in the early morning and lasted about six hours.

The transit of Venus began at 0619 BST and ended at 1224 BST.

1. Image of the early part of the transit of Venus, 8 June 2004. ©National Maritime Museum, Greenwich, London Observers watched the transit using a range of equipment to watch the transit, including specially made solar filter glasses, sometimes called 'eclipse shades'.

The sequence of the transit

Venus is the black dot silhouetted against the bright disk of the Sun.

1. Early part of the transit sequence. This picture was taken in the early morning.

2: Solar image in the middle stage of the transit of Venus, 8 June 2004. ©National Maritime Museum, Greenwich, London. 2. Middle part of the transit sequence. This picture was taken in mid-morning.

3. Later part of the transit sequence. This picture was taken towards late morning.

The transit of Venus in history

The transit was observed in the 18th and 19th centuries in the hope that it could be used to find the size of the Solar System.

Captain James Cook is perhaps the transit's most famous observer. His first voyage to the Pacific took place in 1768 so he would be ready to observe the 1769 transit.

3: Solar image in the later stage of the transit of Venus, 8 June 2004. ©National Maritime Museum, Greenwich, LondonJeremiah Horrocks on 24 November 1639 became the first man to observe and record a transit of Venus. He managed this at the age of 21 by making more accurate calculations of when it would be visible than any astronomer before him. Horrocks made his observations in Hoole, a town 15 miles north of Liverpool. He was the son of a farmer and had grown up in a small village near Liverpool, but even though of a poor family still went to Cambridge aged only 13. He died suddenly at the age of 22 in 1641.

In the 18th century the Royal Society organized Britain's transit expeditions sending ships across the globe. In the 19th century it was the task of the Royal Observatory and its Astronomer Royal, George Biddell Airy. 

Warning – never look at the sun through a telescope or binoculars without a proper solar filter as permanent eye damage can result.